Discovery's businesses include Animal Planet and Discovery Channel, and it operates Oprah Winfrey's OWN Network under a joint venture.

On the distribution side, the cable industry has been a hotbed of potential merger activity. The latest target is Time Warner Cable, which is being circled by competitors Comcast and Charter Communications. (Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.)